The Russians aren't slowing down either
Their's look a bit taller, but height doesn't concern them apparently. I think David Christiansen wanted RD-180s under an ET derived SLS/Direct tankage, but filled with hydrocarbons...
I really hate to hear that about the potential RD-180 ban. That is going to kill Dream Chasers ride, the Atlas V, but they do have rights to start production--it will just take time.
We had a chance to test the Soviet Energiya equivalent to SSME, the RD-0120, which was actually trouble free, as compared with RD-170, what with burn throughs, etc.
The RD-0120 used channel wall. I really wish we had been allowed near those, to see them and work with them.